Techno-Economic and environmental assessment of Biogas digestate for solid biofuel production.

Abstract

This study evaluated the techno-economic and environmental viability of a briquette production project from digestate. The objectives were to assess the quality of briquettes, estimate the cost of production, determine the feasibility of the project, and carry out a lifecycle analysis of the production process. Production cost was estimated from the market price of commodities and specific economic indicators were used for feasibility analysis. OpenLCA software was used to carry out the life cycle analysis of the process. Sensitivity analysis was performed on some essential input parameters that may affect the profitability of the project and their environmental implications. The experimental procedure carried out produced briquettes with a calorific value of 14.2Mj/kg which meets the universally accepted briquettes standard. The economic analysis of the produced biofuel was analyzed to determine its economic feasibility. For the briquettes production capacity of 193.057 tons/year, the produced briquettes were sold at 0.5 USD per Kg generating a revenue of 96,528.6 USD per year. The total production cost is 61,016.15 USD per year. The net profit is 35,512.45 USD per year. The briquettes production's economic feasibility as analyzed from the investment rate is 53.12%, the payout period is 4.23 years, and the NPV is 361,404.74 USD for 10 years. A cradle to gate system boundary was selected for this study, key areas being: Digestate storage, size reduction, carbonization, briquetting, and transportation of both raw material and final product. The results obtained from OpenLCA software showed that the process contributed to 3.900E5kg of CO2 Eq for the global warming impact category,19.074kg 1,4-DCB-Eq for the human toxicity impact category,1.300E5 moles of H+-eq for the acidification potential impact category, and 4.745-5 kg CFC-11-Eq for the ozone layer depletion impact category. A sensitivity analysis indicated the effects of the transportation system and energy source on the life cycle’s environmental impact.